Polymorphism of heterochromatic regions of flax chromosomes

The C-banding technique was used to study flax chromosomes (Linum usitatissimum L., 2n = 30). Heterochromatin was located mainly in pericentromeric regions of chromosomes. In spite of small size (1.5-3.5 microm), all 15 pairs of homologous chromosomes were identified on the basis of the C-banding pattern and morphology. An idiogram of C-banded chromosomes of L usitatissimum L. is presented. Polymorphism of chromosomal heterochromatic regions was studied in karyotypes of three flax samples: L usitatissimum L., accession K-603 (L usitatissimum var. usitatissimum), and accession K-594 (L. usitatissimum var. humile (Mill.)). A common C-banding pattern was observed in all forms studied, although there were some distinctions in the individual band size. The fibre flax (accession K-603) karyotype had the C-banding pattern similar to that of L usitatissimum L., but some intercalary and telomeric C-bands were somewhat larger, and a satellite (NOR) was observed in the short arm of chromosome I. In crown flax, (K-594) chromosomal C-banding pattern exhibited smaller pericentromeric and larger intercalary bands; telomeric bands were present on almost all chromosomes. Thus, the intraspecies polymorphism revealed in the chromosomal C-banding pattern makes possible the use of C-bands as chromosome markers in the studies of genetic and genomic polymorphism of this species.     

Chromosomal studies on five species of the genus Leptodactylus Fitzinger, 1826 (Amphibia, Anura) using differential staining

Cytogenetic studies were carried out on five species of Leptodactylus, namely L. fuscus, L. notoaktites, L. labyrinthicus, L. ocellatus, and L. podicipinus, after standard staining, Ag-NOR and C-banding as well as BrdU incorporation for three of them. The species had 2n = 22 chromosomes and two basic karyotype patterns. Chromosome 8 was a marker bearing a secondary constriction. In all species, this secondary constriction corresponded to the Ag-NOR site. The species had centromeric C-bands in all chromosomes of the complement, but some interstitial or telomeric bands seemed to differentiate some karyotypes, either at the species or the population level. In L. ocellatus, the C-banding pattern confirmed the occurrence of a heteromorphic pericentric inversion in chromosome 8 in specimens from one of the populations. The BrdU incorporation technique showed no detectable difference in the replication patterns of the major bands in the chromosomes of L. notoaktites, L. labyrinthicus, and L. ocellatus.     

C-banded karyotypes of two Silene species with heteromorphic sex chromosomes.

Mitotic metaphase chromosomes of Silene latifolia (white campion) and Silene dioica (red campion) were studied and no substantial differences between the conventional karyotypes of these two species were detected. The classification of chromosomes into three distinct groups proposed for S. latifolia by Ciupercescu and colleagues was considered and discussed. Additionally, a new small satellite on the shorter arm of homobrachial chromosome 5 was found. Giemsa C-banded chromosomes of the two analysed species show many fixed and polymorphic heterochromatic bands, mainly distally and centromerically located. Our C-banding studies provided an opportunity to better characterize the sex chromosomes and some autosome types, and to detect differences between the two Silene karyotypes. It was shown that S. latifolia possesses a larger amount of polymorphic heterochromatin, especially of the centromeric type. The two Silene sex chromosomes are easily distinguishable not only by length or DNA amount differences but also by their Giemsa C-banding patterns. All Y chromosomes invariably show only one distally located band, and no other fixed or polymorphic bands on this chromosome were observed in either species. The X chromosomes possess two terminally located fixed bands, and some S. latifolia X chromosomes also have an extra-centric segment of variable length. The heterochromatin amount and distribution revealed by our Giemsa C-banding studies provide a clue to the problem of sex chromosome and karyotype evolution in these two closely related dioecious Silene species.     

Comparison of the Giemsa C-banded karyotypes of Hystrix coreana and H. patula (Poaceae, Triticeae)

The karyotypes of Hystrix coreana from eastern USSR and H. patula from USA were investigated by Giemsa C-banding. Both species are outbreeders and have 2n = 4x = 28. The karyotype of two plants of H. coreana has 10 metacentric, 6 submetacentric, 8 heterobrachial and 4 SAT chromosomes; two plants differed by having 12 metacentric, 4 submetacentric, 8 heterobrachial and 4 SAT-chromosomes, and 10 metacentric, 4 submetacentric, 9 heterobrachial and 5 SAT-chromosomes, respectively. The C-banding pattern had no or few inconspicuous intercalary bands, but conspicuous telomeric C-bands in one or both arms giving a high content of heterochromatin (16.3–18.2%). The chromosome complement of one plant of H. patula had 8 metacentric, 6 submetacentric, 8 heterobrachial and 6 SAT-chromosomes. The C-banding pattern had between 1 and 4 intercalary or centromeric bands and conspicuous telomeric bands on one or both arms giving a high content of constitutive heterochromatin (16.4%).     

Composition of constitutive heterochromatin of Pseudonannolene strinatii Mauriès, 1974 (Diplopoda, Spirostreptida) analyzed by AT/CG specific fluorochromes

Triple staining with fluorochromes (DA/DAPI/CMA) and C-banding were used to characterize the composition of Pseudonannolene strinatii heterochromatin. C-banding showed C+ bands of different labeling intensity on chromosomes 1 and 2 in some cells. Fluorochrome staining revealed DAPI+ regions corresponding to the C-banding pattern, indicating that the heterochromatin of this species is abundant in AT-rich sequences.     

Heterochromatin patterns in triatomines of the genus Panstrongylus

Spermatogenesis was analysed by C-banding in two species of triatomines, Panstrongylus megistus and P. herreri. Both species revealed interstitial and terminal bands in the autosomes, which is a common pattern in Heteroptera. The terminal bands corroborated the hypothesis that in holocentric chromosomes the heterochromatin is preferentially located at the telomere. The sex chromosomes in P. herreri were totally heterochromatic in spermatogenesis, and in P. megistus the X chromosomes alternated between positive and negative banding.     

Computer assisted karyotype analysis of Pyrrhopappus carolinianus

With the help of Computer Aided Karyotyping procedures, Ag-NOR staining and C-banding techniques, the karyotype of Pyrrhopappus carolinianus (Asteraceae, Lactuceae) has been studied. The species has 2n=12 chromosomes. Silver staining reveals that the two shortest pairs of chromosomes possess NOR's. On the basis of chromosome length and centromere position, only the longest chromosome pair and the satellite chromosomes can be identified. Two types of C-banding can be obtained, dependent on the temperature of the hydrochloric acid hydrolysis of the root tips. Hydrolysis at 60°C results exclusively in centromeric bands, whereas a treatment at room temperature reveals a pattern of intercalary bands. A computer assisted analysis of the intercalary banding pattern resulted in the construction of schematic representation of the average C-banding pattern. This banding pattern allows an easy identification of each of the chromosome pairs.     

Constitutive heterochromatin DNA polymorphisms in diploid Medicago sativa ssp. falcata.

A Giemsa C-banding technique was used to study the amount and location of constitutive heterochromatin in diploid (2n = 2x = 16) Medicago sativa ssp. falcata (L.) Arcangeli. Most accessions had the standard C-banding pattern with centromeric bands on all the chromosomes and a prominent heterochromatic band at the nucleolar organizer regions (NOR) of the satellited (SAT) chromosomes. However, we observed in various accessions that constitutive heterochromatic C-bands can exist at the telomeric ends of all the chromosomes. Interstitial bands occurred on the short arms of all chromosomes except for chromosome 3 and on the long arms of chromosomes 1, 2, 3, and 6, only. Rearranged chromosomes such as isochromosomes have been observed for the short arms of chromosomes 2 and 6. This is the first report on the existence of C-banding polymorphisms and the detection of putative isochromsomes in the chromosomes of diploid ssp. falcata which could have contributed to the variation observed in cultivated alfalfa.     

C- and G-bands of the opossum chromosomes: terminal sequences of DNA replication.

The sex chromosomes of the opossum, Didelphys virginiana, are the only elements that exhibit C-banding. In contrast, the sex chromosomes as well as the autosomes bear specific G-Bands. However, unlike other mammalian species different types of G-banding are observed if the chromosomes are pretreated with trypsin and SSC solution The SSC-pretreated chromosomes show discrete bands only when stained with Giemsa at certain pH values. An asynchronous pattern of terminal DNA replication is observed among the three C-banding regions of the X-chromosome. The inter- and intrapositive G-banding areas of the chromosomes are not always late in DNA replication in comparison to those negatively stained G-banding areas.     

玉米花粉单倍体植株染色体上异染色质的变异

我们用Giemsa BSG C-带技术检查了玉米花药培养获得的花粉单倍体植株根尖细胞染色体上异染色质的变异,观察结果表明,有的植株所显示的C-带数目是与供体植株的相一致,有的植株所显示的C-带数目则发生了显著变化,其中有的增加,有的减少。并讨论了异染色质发生变异的可能原因。还相应地观察到间期核中染色中心的变化是与中期染色体上C-带数目的变化相一致。     

A Modified Giemsa C-Banding Technique For Hordeum Species

A Giemsa C-banding technique with a hot 1 N HCI hydrolysis step has been developed for barley chromosomes. This step makes it easy to obtain well separated C-banded chromosomes. To compare this technique with other C-banding techniques, chromosomes of H. vulgare cv. York were stained by both this technique and a modification of the technique of Kimber et al (1976). With respect to centromeric and intercalary bands, both techniques produce a similar banding pattern, but telomeric bands observed by the modified technique of Kimber et al (1976) were not detected by our procedure. This indicates that telomeric heterochromatin may be different chemically and/or structurally from the centromeric and intercalary heterochromatin and its appearance dependent upon the C-banding technique. The procedure described provides a relatively rapid technique for C-banding of barley chromosomes.     

Comparison of the chromosomes of Triticum timopheevi with related wheats using the techniques of C-banding and in situ hybridization

Summary The chromosomes of the tetraploid wheats Triticum timopheevi (Genome AAGG) and T. araraticum (Genome AAGG) were C-banded at mitosis. The identity of the banded and unbanded chromosomes was then established by firstly making comparisons with the hexaploid species T. zhukovskyi which has the genome formula AAAAGG. Secondly, the meiotic pairing in F₁ hybrids between T. timopheevi and diploid wheats was examined by means of C-banding. The results showed that the banded chromosomes belonged to the G genome, while the unbanded chromosomes belonged to the A genome. Only one of the two pairs of satellited chromosomes had strong heterochromatic bands. The relationship between the genomes of T. timopheevi and T. dicoccum (Genome AABB) was then assessed at meiosis in hybrids between these species, using the techniques of C-banding and in situ hybridisation of a cloned ribosomal RNA gene probe. It was concluded that there were differences both in the amount and distribution of heterochromatin and also translocation differences between the species.     

Giemsa C-banded karyotypes of two subspecies ofHordeum brevisubulatum from China

C-banding patterns ofH. brevisubulatum subsp.brevisubulatum (2x) and subsp.turkestanicum (4x) had conspicuous telomeric C-bands in at least one chromosome arm with a minor difference in average band size between subspecies. Other conspicuous bands were few in number as in other taxa of the species complex. The C-banded area of the chromosomes was estimated to be 7 to 8 and 6 per cent, respectively. C-banding- and SAT-chromosome polymorphisms were observed in both subspecies. The latter and previous observations indicate that the number of SAT-chromosomes is a less reliable diagnostic character. Nucleolar organizer region polymorphisms were demonstrated through silver nitrate staining of nucleoli. C-banding patterns corroborated that tetra- and hexaploid cytotypes of subsp.turkestanicum form an autopolyploid series. Reliable identification ofH. brevisubulatum taxa based on cytological criteria should include the simultaneous use of C-banding patterns, and number and morphology of marker chromosomes.     

Comparisons between C-banding Patterns on Root Tip Chromosomes of Different Cultivars in Maize( Zea mays)

The technique of Giemsa banding, C-banding patterns on the root tip chromosomes and the chromocentres of interphase nuclei with three eultivars (Dai Zi Bai, Qun Dan 105 and 2×6) of maize were studied. The results are as follows: 1. After fixation and treatment in a saturated solution of barium hydroxide the preparations were incubated in 0.5×SSC, I×SSC, 3×SSC, 4×SSC or distilled water respectively forⅠ h at 60 ℃ and the other steps in C-banding procedure were not changed so as to find the optimum saline concentration for Giemsa banding in maize. The experimental results shown that 0.5×SSC was the best. But bands could not produced very well by treating samples in distilled water. 2. There were terminal, subterminal and centric bands in Dai Zi Bai and Qun Dan 105. The C-banding patterns on the root tip chromosomes of these two cultivars were different from each other. Qun Dan 105 had 10 prominent bands in total, while Daf Zi Bai had 7. The banding patterns of each chromosome were described in detail. 3. The average chromocentres per cell in Dai Zi, Qun Dan 105 and cultivar 2×6 were 7.1, 10.9 and 7.2 respectively. Their prominent band numbers on the chromosomes were 7, 10 and 8 correspondingly. It seems that the number of C-bands on the chromosomes is close to that of chromocentres.     

Identification of the pattern of heterochromatin distribution in Passiflora species with C-banding

We tested four C-banding protocols to obtain heterochromatic bands in the passion fruit species Passiflora edulis and P. cacaoensis (Passifloraceae). Three of these protocols had been previously described. The three published protocols were not adequate to obtain C-bands in these species. An adapted protocol demonstrated heterochromatin distribution in metaphasic chromosomes of species of Passiflora for the first time. The differentiated coloration for C-bands was obtained with immersion of the slides in 99% ethanol, 45% acetic acid (additional step), 0.2 N hydrochloric acid, hydroxide of barium, 45% acetic acid, and 2X standard saline citrate at four different temperatures. The C-bands were observed in the satellites and in the telomere and centromere regions of all chromosomes, both in P. edulis and in P. cacaoensis.     

Giemsa C-banded Karyotypes of Eight Species of Alstroemeria L. and Some of Their Hybrids

Karyotype analysis of Alstroemeria angustifolia ssp. angustifolia,A. aurea, A. inodora, A. ligtu spp. ligtu, A. magnifica ssp.magnifica, A. pelegrina, A. philippii and A. psittacina usingFeulgen-staining and Giemsa C-banding techniques revealed foreach species a characteristic chromosome morphology and C-bandingpattern. These characteristics could be used to identify manyindividual chromosomes in diploid interspecific hybrids. Besidesinterspecific variation, some degree of intraspecific variationin C-banding pattern was observed within A. angustifolia ssp.angustifolia, A. aurea, A. ligtu ssp. ligtu, A. magnifica ssp.magnifica and A. philippii . All species had large chromosomes (2 n =2 x =16) and asymmetrickaryotypes. In many species the short arms of the acrocentricchromosomes were darkly stained upon Giemsa C-banding. Thesetelomeric bands seemed satellites. B-chromosomes were observedin one species, A. angustifolia ssp. angustifolia . A variablenumber of large intercalary and telomeric C-bands was presentin the Chilean species, whereas the Brazilian species showedonly small C-bands. The differences in karyotypes suggest anearly separation of the Chilean and Brazilian species, afterwhich speciation followed different evolutionary pathways. InAlstroemeria the Giemsa C-banding technique can be valuableto plant taxonomists for unravelling species relationships. Alstroemeria ; Inca lily; evolution; Giemsa C-banding; karyotype     

The role of chromosomal proteins in the C-banding of Allium cepa chromosomes.

When chromosomes of Allium cepa are subjected to a C-banding procedure (incubation in saturated barium hydroxide followed by phosphate buffer at 60 degrees C for 1 h) and then treated with Giemsa stain, bands appear at the telomeres of all chromosomes. Microspectrophotometric measurements of Feulgen-DNA content, demonstrated that the C-banding procedure extracted DNA from the nuclei. Staining of banded chromosomes with several DNA-specific stains showed that this loss was differential, with the band DNA exhibiting more resistance to extraction than that of the rest of the chromosome. The C-banding procedure did not extract chromosomal proteins, however, and no difference in mass per unit length could be detected by Nomarski optics between band and interband regions. Several experiments demonstrated that chromosomal proteins play a significant role in C-banding. First, treatment of chromosomes with pronase before C-banding resulted in the elimination of differential staining with Giemsa. Furthermore, in preparations where the DNA was completely hydrolysed with hot TCA, the remaining chromosomal proteins were found to exhibit a differential affinity for Giemsa stain. Amido black staining demonstrated that total chromosomal protein was uniformly distributed after the hot TCA digestion, but the proteins localized in the telomeres had a greater affinity for the Giemsa stain than the bulk of the chromosomal proteins. When the TCA-digested chromosomes were subjected to the C-banding procedure before staining, the differential affinity of the telomeres for the Giemsa stain was lost. Thus, C-banding appears to be the result of a complex interaction between protein and DNA in which the greater resistance to extraction of the band DNA is necessary to stabilize and preserve chromatin protein which exhibits a differential affinity for Giemsa stain.     

部分柑桔属及其近缘属Giemsa C-带带型研究

本文应用Giemsa显带技术研究了枳属(Poncirus)、金柑属(Fortunella)和柑桔属(Citrus)16个分类群的染色体。枳属以末端带和着丝点带为主,金柑属与柑桔属主要以末端带为主;统计分析了各分类群每对染色体及全组染色体的异染色质含量,并列出其带型公式;探讨了金柑属的分类学地位;赞同把柚(C.grandis)作为柑桔属的基本种之一;根据异染色质含量的变化对柑桔属的带型演化进行了讨论。     

The Basic Karyotype of Lotus tenuis C-banding and Feulgen Studies

The basic karyotype of L. tenuis is illustrated. The study ofFeulgen stained metaphases has shown that the chromosome complementconsists of four pairs of median chromosomes and two pairs ofsubmedian chromosomes. Two nucleolar constrictions characterizethe first homologous pair. The C-banding pattern includes largepericentric bands in each chromosome pair and a terminal bandin the short arm of chromosome 3 Lotus tenuis, chromosome morphology, C-banding     

Cytological characterization of heterochromatin and rDNA inPinus radiata andP. taeda

Fluorochrome C-banding ofPinus radiata andP. taeda metaphase chromosomes showed many pericentromeric DAPI bands and interstitial CMA bands inP. radiata, and centromeric and interstitial CMA bands inP. taeda. Giemsa C-band patterns differed between the species with centromeric bands inP. radiata but no consistent bands inP. taeda. A karyotype ofP. radiata was developed based on banding patterns that distinguished all but two of the 12 pairs of chromosomes. In situ hybridization (ISH) using probes for high-copy ribosomal DNA (rDNA) showed 10 pairs of 18S–25S sites and two pairs of 5S sites in both species. Most of the sites were interstitial or centromeric.